Aetius was the most powerful general in West (magister militum) from 433 until his death in 454.
His greatest opponent was Attila (q.v.) and his greatest victory was the defeat of a Hunnic army under Attila in 451 at the battle of the Catalaunian Fields (q.v.). As a young man he spent years as a hostage to the Huns (q.v.), forming a friendship with
King Rugila, Attila’s uncle and predecessor. His most reliable troops in the defense of Gaul against the Germans were Huns, and, moreover, Aetius himself married a German bride. Valentinian III (q.v.) assassinated him in 454, despite his loyal service. Such were the ironies of Aetius’s career, ironies that reveal the complexity of Germano- Roman relations in the fifth-century West.
(Source: «Historical Dictionary of Byzantium», by John H. Rosser)